1. Field of the Invention
The present invention generally relates to fluid actuated downhole tools. More particularly, the invention relates to a locator used in conjunction with a pumping apparatus used for activating downhole tools by providing pressurized fluid. More particularly still, embodiments of the invention pertain to a locator for a reciprocating hydraulic slickline pump.
2. Description of the Related Art
It is often necessary to deploy and actuate downhole equipment and tools, including packers and bridge plugs, during the completion or remediation of a well. Downhole hardware may be deployed and actuated using various conveying members including drill pipe, coiled tubing or spoolable line, such as wireline and slickline. Drill pipe and coiled tubing are physically larger and have greater strength than wireline and slickline. However, the cost and time requirements associated with procuring and running drill pipe or coiled tubing are much greater than those of spoolable line. Therefore, whenever appropriate, use of spoolable line is preferred.
Wireline and slickline are among the most utilized types of spoolable line. Wireline consists of a composite structure containing electrical conductors in a core assembly which is encased in spirally wrapped armor wire. Typically, wireline is used in applications where it facilitates the transportation of power and information between downhole equipment and equipment at the surface of the well.
Slickline, on the other hand, is mainly used to transport hardware into and out of the well. Slickline, designed primarily for bearing loads, is of much simpler construction and does not have electrical conductors like those in wireline. Instead, slickline is a high quality length (sometimes up to 10000 feet or more) of wire which can be made from a variety of materials, (from mild steel to alloy steel) and is produced in a variety of sizes. Typically, slickline comes in three sizes: 0.092; 0.108; and 0.125 inches in diameter. For larger sizes, a braided wire construction is utilized. The braided wire, for all practical purposes, has similar functional characteristics as a solid wire. Such braided wire is considered to be slickline herein.
As stated above, use of wireline and slickline for deploying and actuating downhole tools is preferred over the use of drill pipe and coiled tubing due to the relatively low expense. Further, use of slickline is preferred over wireline, because slickline based systems are simpler and less expensive than wireline.
When performing operations within a wellbore it is often necessary to know the location of the tool. In wireline and slickline operations it is common to measure the amount of line extended into the wellbore. This is typically done by passing the line over a calibrated measuring wheel at the surface of the well. As the tool is deployed, the length of the line unspoolled into the well is monitored and used as an estimate of tool depth. Stretch and twisting of the line downhole can cause inaccuracies in measured versus actual depth. Such inaccuracies can make it difficult to know the exact depth of the tool. Further, when running tools to a destination downhole, it is advantageous to know the location of the nearest casing coupling, which cannot be determined accurately by measuring the amount of cable let out at the surface.
When setting a packer to seal a wellbore it is advantageous that the packer sets in the smooth inner diameter of the casing, and not at a casing coupling. The inner diameter at a casing coupling is irregular and larger than the inner diameter of the rest of the casing. Thus, if a packer sets at a casing coupling the seal is often in jeopardy due to the inner diameter irregularities.
It is known to use locators in conjunction with a tool lowered on the wireline. These locators are often collets which send data to an operator at the surface. The collet informs the operator of the location of casing couplings as the tool reaches them. Thus an operator may record the location of the casing couplings in conjunction with the unspoolled line to get a more accurate determination of depth.
Many of the tools deployed during well completion and remediation, such as packers and bridge plugs, for example, are actuated by increased fluid pressure in the wellbore or by explosives. Often, downhole electric pumps are utilized to provide the increased pressure. Use of electric pumps run on wireline is common, but the pumps are complex and very expensive.
Therefore, there is a need for a locator for use in conjunction with a simple and reliable hydraulic pump that can be run on slickline and can be used to deploy hydraulically actuated tools. There is a further need for the pump to be operated by axially reciprocating the slickline.